Piezo-electric crystal system



Aug. 23, 1927.

A. H. TAYLOR PIEZO ELECTRIC CRYSTAL SYSTEM Filed July 29. 1925 Patented Aug. 23, 1927.

UNI-TED STATES v 1,639,817 PATENT OFFICE.

man's. n. TAYLOR, or wnsnrue'ron, msraxor or oonomam, nssreuon '10 wmnn mm, mm, or'unw YORK, N. Y.,

A CORPORATION OF DELAWARE.

PIEZO-ELECTRIC CRYSTAL SYSTEM.

Application filed July 29, 1925. Serial No. 46,802.

My invention relates broadly to piezo electric crystal circuits and more particularly to a piezo electric crystal system for electron -tube circuits. a

One of the objects of my invention is to provide an attachment for radio receivers by which the constant frequency oscillating properties of crystals may be employed for accurately tuning the receiving set to a desired frequency.

. Another object of my invention is to provide a constant frequency calibration attachment for electron tube circuits wherein a plurality of different frequencies may be selected and the electron tube circuits adjusted in accordance with the selected frequency.

Still another object of my invention is to provide a crystal control system for electron tube circuits in which a plurality of crystals may be independently utilized for adjusting the electron tube circuits at the fundamental frequency of the crystals without interference from quencies 0 other crystals associated with the electron tube circuits. A further object of my invention is to provide a constructin of crystal holder by which a plurality of crystals each having different fundamental frequencies may be electrically associated with an electron tube system for adjusting the electron tube system for operation at a particular frequency.

A still further object of my invention is to provide an attachment for radio receivers which may be readily applied to existing types of receivers in order to adjust the receiving circuit for a particular signaling frequency to facilitate picking up of signaling energy being transmitted at a, known frequency or wave length.

My invention will be more clearly under- I stood from the specification hereinafter following by reference. to the accompanying drawings, in which:

Figure 1 is a plan view showing one construction-"of the crystal attachment for receivers; Fig. 2 is. a cross-sectional view through the construction illustrated in Fig. 1; Fig. 3 illustrates the application of my invention to a radio receiving circuit; and Fig. 4 is a diagrammatic view illustrating the method of adjusting an electron tube circuit at the, fundamental frequency of a particular crystal.

artials or the fundamental fre-' My invention may be explained by consideringthe secondary circuit of a typical receiver using adjustable regeneration. and permitting continuous wave reception. If a quartz crystal provided with upper and lower metallic contact plates is connected across the input circuit of the electron tube system of the receiver as represented in Fig. 4 and in the position indicated in the holder illustrated in Fig. 2, the upper contact plate to grid, and the lower to filament, a very large number of resonance clicks will be found as the tuning of the circuit is altered over a wide range of frequencies. This effect occurs when the crystal has comparatively large area adjacent the contact plates and when the main crystal oscillation corresponds to the thickness of the crystal. The resonance clicks are very numerous and very strong around this main oscillation. By the-main oscillation is meant that oscillation which the crystal would normally genprincipal modes of oscillation, some of them occurring very far away from the fundamental oscillation but are not true harmonies and should be called partials. For any given crystals these oscillations may be sufliciently constant but they are so complicated and some of them are so close together that serious problems are offered when it is attempted to find a satisfactory method for employing the crystals in connection with calibration or accurate setting of a receiver. For example,-if five crystals with fundamental frequencies represented by a, b, 0, (Z, and 6, were consecutively used connected across the input circuit of an oscillator there might be difliculty in distinguishing between the partial of a and the funda-" mental of c or d. Experimental work has shown definitely thatsuch an ambiguity than the t ickness oscillation, the number of additional oscillations is reduced to certain well defined partials, none of them too close to the fundamental and it becomes ossible to utilize the main oscillations and t e partials, if desirable, for the purpose of callbrating and for accurately setting the C11- cuits'of a radio receiver. The device of my invention has been developed in sufficiently small dimensions to readily attach to substantiall any type of radio receiver without radical y changing'its design and in some cases, without redesigning at all. My invention has been successfully employed in connection with the mtermediate range receiver of the United States Navy Department. By reason of the construct-ion of the device of my invention It 1s possible to make the partials so weak that they are negligible if such a condition is desirable. Suppose, for instance, it Is desired to absolutely fix on the receiver, fourteen dlfferent wavelengths or frequencies. Fourteen crystals may be arranged in a crystal holder and each one will give rise to a sin 1e definite'setting. The crystal holder is esigned for a set of crystals with means to prevent more than one crystal from functioning at the same time and in order to emphasize the fundamental sufficiently without giving rise to partials which mi ht be stron enough to be mistaken for fun amentals. y the use of crystal rods the partials are widely se arated from the fundamental and inter erence is largely eliminated.

Having generally outlined the problem presented by my invention more particular reference w1ll be had to the drawings. The

crystal holder 1 shown in' Fig. 1 is adapted to hold six crystals 2, 3, 4, 5, 6, 7, which lie loosely in narrow ockets 2', 3, 4*, 5 6f, and 7 in the material of the holder 1. It is crystal, nor is it highly desirable, unless it is desired to em hasize the. artials in order to get more t an one call ration point out of a single crystal. The pockets 2, 3", 4", 5, 6', and 7 in the material 1, therefore, do not go clear through the disk. The mate rial 1 may be of any suitableinsulation such as hard rubber and the pockets formed in the disk leaving a thin layer of rubber about one millimeter thick between the rubber disk and the bottom ofthe so-called contact plate 8 which connects to the filament electrode 9 of electron tube 10. The contact plate 8 is shown in the form of a flat annular ring with a lead wire 11 extending therefrom for connection to the filament 9 of tube 10. Each crystal then, lies in its pocket close to, but

.; not touching, the metal plate 8. The crystals are prevented from tumbling out of their mechanically vibrate and must not be 1,ese,a17

disk 1 and carrying a rotating arm 17 with a detent 18, which slips in apertures 19, 20, 21, 22, 23 and 24 in the rubber'disk 1 at the ends of the respective crystals. When the arm 17 is rotated over one of the crystals,- a pronounced click is obtained when the receiver circuit shown in Fig. 3 is tuned past that particular frequency; that is, the frequency corresponding to that crystal. It should be ex lained that these resonance clicks differ rom the small click obtained when two circuits go 'in and out of tune with each other, by having a transient, musical quality which is due to the crystal oscillation existing and differing (by an audible number of beats) from the circuit frequency. This exists only during a very transient period. It is not sible to hold this condition. It is foun however, that the receiver can be set with very great accuracy indeed to a predetermined frequency by this method.

If, however, a number of crystals are in the holder 1 at the same time, even although the arm 17 is not over more than one of the crystals at the same time, the two crystals adjacent. and sometimes all of them, will give weaker, but nevertheless definite clicks This is undesirable and confusing. Therefore, in order to prevent the occurrence of undesirable clicksa metallic guard ring 25 is positioned directly around the central shaft 16 but substantially insulated therefrom and which has spokes or sector portions 26 filling in the surfaces between the crystals. The sectional view of Fig. 2 illustrates the shape of this guard piece which is grounded to connection 11. As shown in Fig. 1 the guard piece 25 has its sector portions extending immediately adjacent the edges of the pockets which house the crystals. The effect of this guard piece 25 is to short-circuit to ground (filament) any electrical flux which spreads out laterally from the rotating arm 17. In

Ill)

other words, it confines the flux to the particular crystal which it is desired to utilize. The crystal holder is comparatively small and compact and can be readily added to substantially any type of radio receiver. For .very low frequencies the crystals may be loaded by cementing steel on to them so that a fairly long wave can be obtained with a relatively short crystal. On the other hand, for high frequency operation more use can be made-of the partials. In this case the upper and lower contact plates are arranged as to actually touch the crystals, as this brings out the partials with greater emphasis. The adjustment of the crystal is obtained by grinding the crystal .to hppropriate dimensions or altering the load on the ends of the same or both.

ating the electron tube system the dials for the tuning controls are calibrated approximately correct so that the receiver may be readily adjusted within approximately ten per cent of the desired wavelength. The regeneration control 30 in the receiving circuit may be adjusteduntil the circuit oscillates comfortably. The, tuning of'the receiver may then be adjusted back and forth until the particular click with a transient musical tone quality, arising from the use of the crystal control is obtained. The tuning controls are stopped at a point where, by a very small movement, they just pass through the click. It will then be found that thereceiver remains within a small fraction of a kilocycle of the desired fretipiency. The adjustment can be made in a ew seconds. and the settings thus obtained are'all of a high order ofaccuracy. A calibration curve can be plotted for the receiver from time to time connecting up the different points obtained from the crystals and thus by interpolation, any desired frequency can be found. It is desirable that the receiver have some means of very fine tuning, if extremely high accuracy is needed, be: cause it is thereby possible to make a setting with very accurate precision.

It will be seen that the device of my invention is readily applicable to .existing designs of receivers and that the crystal control does not interfere in the least with the intensity of the signal since the capacity of the rotating arm 17. connected to grid is extremely small. The receiver may be read- 11y adapted to various wavelengths or frequencies by inserting a different assortmentof crystals inthe crystal holder. The application of the crystals to the receiver circuit facilitates the operation of the receiver enabling the signaling frequency to be read ily picked up and the performance of the receiving circuit is considerably improved by reason of the fact that the circuit is maintained in operation upon a specific frequency determined 'by the crystal.

VVh1le I have illustrated the crystal control system as applied to a receiving circuit, I desire that it be understood that any electron tubesystem may be adjusted by utilizmg the principles of my invention as here- -inbefore set forth. It will be understood that modifications may be made and that no limitations upon the invention are intended other than those imposed by the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is as follows:

1. In an electron tube system the combination of an electron tube having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes. a

plurality of piezo electric crystals each having a different fundamental frequency, and

means for electrostatically associating a selected piezo electric crystal with the input circuit of said electron tube system for predetermining the oscillatory condition thereof.

2. In an electron tube system the combination of an electron tube having grid, fila ment and plate electrodes, an input circuit interconnecting said grid and filament electrodes, an output circuit interconnecting said plate and filament electrodes, and a plurality of piezo electric crystals each having a different fundamental frequency means for individually connecting a selected piezo electric crystal in said input circuit for'adjusting said electron tube system at a selected frequency, and means for preventing inter-action from others. of said crystals which areicut out of said input circuit.

3. An electron tube system comprising in combination an electron tube having grid, filament and plate electrodes. an input circuit interconnecting said grid and filament electrodes, an output. circuit interconnecting said plate and filament electrodes, and a plurality of crystals each having a different fundamental frequency arranged to be cafilament electrodes in said input circuit.

pacitively connected between said grid and 4. An electron tube system comprising in lar crystal in said input circuit, and means" positioned between each of said crystals for preventing inter-action of others of said crystals upon said selected crystal for adjusting said electron tube system at the frequency of the selected crystal.

5. An electron tube system comprising in combination an electron tube having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes,

and a plurality of piezo electric crystals having the longitudinal axis; thereof exceeding the lateral axis thereof, a conductive plate member, means for swinging said plate member over the upper surfaces of each of said crystals in capacity relation thereto for effectively including a selected crystal in the input circuit of said electron tube in such manner that oscillations along the longitudicillations along the longitudinal axis are nal axis are utilized to determine the operation of said input circuit.

6. An electron tube system comprising in combination an electron tube having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, a plurality of piezo electric crystals having the longitudinal axis thereof exceeding the lateral axis thereof, said crystals .being arranged for connection in the input circuit of said electron tube in such manner that osutilized to determine the operation of said input circuit, and means extending between said crystals along the longitudinal axis thereof for preventing more than one crystal acting simultaneously upon said circuit.

7. In an electron tube system the combination of an electron tube having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, a holder for a plurality of piezo electric crystals, connections between one side of each of said piezo electriccrystals and one side of said input circuit, and a movable electrode adapted to be swung over said crystals in capacity relation thereto for electrically connecting the opposite side of a selected one of said crystals with the other side of said input circuit for determining the operation of said electron tube circuit in accordance with the fundamental frequency of a particular crystal:

8. In an electron tube system the combination of an electron tube having grid, filament and plate electrodes, in 'ut and output circuits interconnecting said electrodes, a plurality of piezo electric crystals, circuits connecting said crystals in the input circuit of said electron tube system, said crystals bein arranged closely adjacent each other for utllizing the oscillation corresponding to the length of the crystals, and an electrostatic shield extending between each of said crystals for electrostatically shielding said crystals one from another for preventing the action of several crystals simultaneously when the fundamental frequency of one of said crystals is being utilized to adjust the electron tube circuit.

- 9. Piezo electric crystal apparatus co m.

' prising in combination a piezo electric crys tion, a plurality of pockets inisaid holder for housing piezo electric crystals therein, said pockets eing formed to receive piezo electric crystals each having a longitudinal axis exceeding the lateral axis thereof, and switching means for selecting a particular piezo electric crystal from said plurality of piezo electric crystals for effectively utilizing the oscillations of said particular piezo electric crystal Without interference from oscillations of others of said. piezo electric crystals.

10, Piezo electric crystal apparatus comprising in combination an insulated holder, a plurality of pockets in said holder arranged to receive piezo electric crystals each having a longitudinal axis exceeding the lateral axis thereof, switching means for capacitively connecting a selected one of said piezo electric crystals in an electrical circuit, said switching means being arranged to be moved to a position over each of said crystals for effectively utilizing the frequency of a particular piezo electric crystal independent of the frequency of others of said crystals.

11. Piezo electric crystal apparatus comprising in combination a substantially circular housing for supporting a plurality of piezo electric crystals, a plurality of radially positioned pockets in said housing, a switching -device pivotally mounted centrally, within said housing, a switch arm carried by said switching device, a conductive plate member supported by said switch arm for establishing a capacity connection with a selected one of said crystals for effectively utilizing the oscillations of said crystal independent of the frequency of others of said piezo electric crystals.

12. Piezoelectric crystal apparatus comprising in combination an insu ated holder, a plurality of pockets in said holder arranged to receive piezo electric crystals, each having a different fundamental frequency, switching means for capacitively connecting a selecte one of said crystals in an electrical circuit, a shaft member for rotating said switching means to a position over each of said crystals for effectively utilizing the frequencies of said crystals, and means extending between said pockets forpreventing interference between oscillations of a selected crystal and oscillations by others of said crystals.

- ALBERT H. TAYLOR. 

